Bacterial and fungal communities associated with Tuber magnatum-productive niches.

Truffles are hypogeous ectomycorrhizal fungi of ecological interest for forestry in soils of the northern hemisphere, and of economical relevance for food markets worldwide. The molecular mechanisms that control truffle body formation are largely unknown, as well as the environmental factors that are likely involved. Among the latter, it has been hypothesized that soil-borne communities may have an impact on truffle production. To address this question, we investigated bacterial and fungal communities resident in productive versus adjacent non-productive grounds of the white truffle Tuber magnatum by using PCR-DGGE. Although bacterial communities were generally highly similar across all samples within the grounds, profiles did cluster according to the productivity of circumscribed niches, and a Moraxella osloensis population appeared to be associated with productive sites. Fungal communities revealed several populations, yet showed no obvious patterns in relation to productivity, although Mortierella and Fusarium oxysporum appeared to be more abundant in the productive area. Our results offer a first glimpse into microbial communities thriving in truffle productive niches, and open the question as to whether microbe-mediated mechanisms may facilitate/inhibit truffle fruiting-body production or, vice versa, i.e. whether truffle sporocarps have an impact on the microbes living in the rhizosphere.